A tanker carrying a $100-million cargo of oil shipped from Iraqi Kurdistan is planning to discharge in Texas, bringing a dispute that is central to the future of Iraq as a united country to U.S. soil.

The tanker, United Kalavrvta, is one of four major consignments of oil shipped by northern Iraq's Kurdistan Regional Government since May in defiance of Baghdad. The government claims it has sole authority to market Iraq's natural resources. The shipments represent a gambit by the KRG to carve out a nation for Iraq's 6.5...